/Engine/Source/Runtime/InteractiveToolsFramework/Public/InteractiveGizmoBuilder.h
AUInteractiveGizmoBuildercreates a new instance of an InteractiveGizmo (basically this is a Factory). These are registered with the InteractiveGizmoManager, which callsBuildGizmo(). This is an abstract base class, you must subclass it in order to create your particular Gizmo instance
class UInteractiveGizmoBuilder : public [UObject](API\Runtime\CoreUObject\UObject\UObject)